For hydraulic camshaft adjusting systems, in which the adjustment is realized through the motor oil pressure, the function of the camshaft adjuster is greatly dependent on the temperature of the motor oil. At low temperatures and thus viscous oil, no regulation or adjustment is possible, because the oil can flow not at all or only very slowly through the oil lines to the adjuster or away from the adjuster. A high oil pressure is achieved but no or only minimal volume flow. At high temperatures, the opposite occurs. The oil is very thin, which causes a large amount of leakage. Therefore, high pressure is not established and only slow adjustment can be realized or the set position can be maintained only poorly. In addition, the oil pressure and thus the function of the camshaft adjuster depends on the engine speed of the internal-combustion engine. In contrast, electric camshaft adjusters function independent of oil pressure. Therefore, the previously discussed problems do not occur, so that the operating range and the operating reliability of the adjuster are increased.
In DE 41 10 195 A1, an adjusting device for electrical adjustment of the relative position of the angle of rotation of two shafts, especially a camshaft in relation to a crankshaft of an internal-combustion engine, with an adjusting gear mechanism formed as a triple-shaft gear mechanism is disclosed, which comprises a crankshaft-fixed driving part, a camshaft-fixed driven part, and an adjusting shaft connected in a torsion-proof manner to an adjusting-motor shaft of an electric adjusting motor, wherein the adjusting motor is formed as a brushless DC motor with a housing-fixed stator and a permanent magnet rotor. The adjusting gear mechanism is formed as a planetary gear mechanism, whose self-locking is mentioned multiple times and is emphasized as an advantage.
However, such self-locking produces disadvantages in terms of the adjusting speed and the necessary adjusting energy. In addition, the unbalanced eccentric drive leads to non-quiet running when the adjusting motor is working.